DB-25

The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems.

A D-sub contains two or more parallel rows of pins or sockets usually surrounded by a D-shaped metal shield that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference. The part containing pin contacts is called the male connector or plug, while that containing socket contacts is called the female connector or socket. The socket's shield fits tightly inside the plug's shield. Panel mounted connectors usually have threaded nuts that accept screws on the cable end connector cover that are used for locking the connectors together and offering mechanical strain relief. Occasionally the nuts may be found on a cable end connector if it is expected to connect to another cable end (see the male DE-9 pictured). When screened cables are used, the shields are connected to the overall screens of the cables. This creates an electrically continuous screen covering the whole cable and connector system.

The D-sub series of connectors was introduced by Cannon in 1952. Cannon's part-numbering system uses D as the prefix for the whole series, followed by one of A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets, followed by either P (plug or pins) or S (socket) denoting the gender of the part. Each shell size usually (see below for exceptions) corresponds to a certain number of pins or sockets: A with 15, B with 25, C with 37, D with 50, and E with 9. For example, DB-25 denotes a D-sub with a 25-position shell size and a 25-position contact configuration. The contacts in each row of these connectors are spaced 326/3000 of an inch apart, or approximately 0.1087 inches (2.76 mm), and the rows are spaced 0.112 inches (2.84 mm) apart; the pins in the two rows are offset by half the distance between adjacent contacts in a row. This spacing is called normal density. The suffixes M and F (for male and female) are sometimes used instead of the original P and S for plug and socket.

Later D-sub connectors added extra pins to the original shell sizes, and their names follow the same pattern. For example, the DE-15, usually found in VGA cables, has 15 pins in three rows, all surrounded by an E size shell. The pins are spaced at 0.090 inches (2.3 mm) horizontally and 0.078 inches (2.0 mm) vertically, in what is called high density. The other connectors with the same pin spacing are the DA-26, DB-44, DC-62, DD-78 and DF-104. They all have three rows of pins, except the DD-78 which has four, and the DF-104 which has five rows in a new, larger shell. The double density series of D-sub connectors features even denser arrangements and consists of the DE-19, DA-31, DB-52, DC-79, and DD-100. These each have three rows of pins, except the DD-100, which has four.

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